Rechargeable batteries are used in a variety of industrial and commercial applications such as fork lifts, golf carts, uninterruptible power supplies, pure electric vehicles and hybrid electric vehicles. Vehicular applications include applications related to propulsion as well as applications related to starting, lighting and ignition.
One aspect of battery operation that is particularly important for electric vehicle and hybrid vehicle applications is that of thermal management. In both electric and hybrid vehicle applications individual electrochemical cells are bundled together in close proximity. Many cells are both electrically and thermally coupled together. Therefore, the batteries used in these applications may generate significant heat during operation. Sources of heat are primarily threefold. A first source is ambient heat due to the operation of the vehicle in hot climates. A second source is resistive or I2R heating on charge and discharge of the cells, wherein I represents the current flowing into or out of the cell and R is the resistance of the cell.
A battery generates Joule's heat and reaction heat due to electrode reaction at charging and discharging operations. A module battery including a series of cells having such a large capacity or a pack battery including a series of the module batteries is configured of several tens to several hundreds of the cells arranged contiguously to each other. The cells, with an increased electric capacity and sealed configuration, increase in the amount of heat accumulation. As a result, heat dissipation out of the battery is retarded and the generated heat is accumulated within the battery.
Efficient thermal management is the key for safety, performance and extended life of battery packs. Battery cells are typically required to be packaged in the available envelop so that maximum temperature of the cells are within specific temperature maximum, with minimal temperature variation amongst the individual cells in the battery pack.
Currently there exists a need in the art for a battery pack that maintains uniform temperature distribution on the cells with optimal minimum peak temperatures, and the least pressure drop associated with the air flow. Minimizing the peak temperature of the cells is important because it increases the life of the cells. Maintaining uniform temperature across the battery is necessary to maintain the pack performance and longevity. The present invention overcomes the deficiencies of prior art using efficient cell packaging and battery pack design so that the temperatures and system pressure drops are within the optimal operational values.